1. Field of the Invention
The present invention relates to a zoom lens, and a zoom lens apparatus using the same.
2. Description of the Related Art
A zoom lens such as a zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2007-212830 and a zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2010-191336, has hitherto been proposed as a large-aperture telephoto zoom lens of class F2.8. The zoom lens in Japanese Patent Application Laid-open Publication No. 2007-212830 is a four-unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, and a positive refractive power. At the time of zooming, a second lens unit and a third lens unit move. Moreover, focusing is carried out by dividing a first lens unit into a front unit and a rear unit, and by moving the rear unit.
According to such an arrangement, in the zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2007-212830, by an interchangeable lens application, at the time of zooming, a focal length changes from 50 mm to 150 mm, and an F-number is about 2.8 in an overall zoom range.
Moreover, the zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2010-191336, is a five-unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, a negative refractive power, and a positive refractive power. In the zoom lens according to Japanese Patent Application Laid-open Publication No. 2010-191336, at the time of zooming, lens units from a second lens unit up to a fourth lens unit move. Moreover, at the time of focusing, the third lens unit is to be moved.
According to such an arrangement, in the zoom lens according to the Japanese Patent Application Laid-open Publication No. 2010-191336, by an interchangeable lens application, at the time of zooming, a focal length changes from 70 mm to 200 mm, and an F-number is about 2.8 in an overall zoom range.
In both the arrangements, the first lens unit is fixed and let to be static so that a balance of weight at the time of zooming is not disturbed. Moreover, for focusing, an inner focusing method is adopted. Focusing at an object at a close distance is carried out by the inner focusing. By devising such method, operability is improved. However, with regard to small-sizing of the zoom lens, it is insufficient.
On the other hand, in Japanese Patent Application Laid-open Publication No. 2012-47814, Japanese Patent No. 5068238, and Japanese Patent Application Laid-open Publication No. 2011-232624, small-sized telephoto zoom lenses have been disclosed. The zoom lens in Japanese Patent Application Laid-open Publication No. 2012-47814 is a six-unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, a negative refractive power, a negative refractive power, and a positive refractive power. In the zoom lens according to Japanese Patent Application Laid-open Publication No. 2012-47814, at the time of zooming, a second lens unit, a fourth lens unit, and a fifth lens unit move. Moreover, for focusing at an object at a close distance, the fourth lens unit and the fifth lens unit are moved independently.
According to such an arrangement, in the zoom lens disclosed in Japanese Patent Application Laid-open Publication No. 2012-47814, by an interchangeable lens application, at the time of zooming, a focal length changes from 45 mm up to 175 mm, and an F-number is in a range of 4˜5.6 in a zoom range.
The zoom lens in Japanese Patent No. 5068238 is a five unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, a positive refractive power, and a negative refractive power. In the zoom lens according to Japanese Patent No. 5068238, at the time of zooming, a first lens unit, and lens units from a third lens unit to a fifth lens unit move.
According to such an arrangement, in the zoom lens disclosed in Japanese Patent No. 5068238, by an interchangeable lens application, at the time of zooming, a focal length changes from 80 mm to 400 mm, and an F-number is in a range of 4.5˜5.6 in a zoom range.
Moreover, the zoom lens according to Japanese Patent Application Laid-open Publication No. 2011-232624 is a four unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, and a negative refractive power. In the zoom lens according to Japanese Patent Application Laid-open Publication No. 2011-232624, at the time of zooming, each lens unit moves.
According to such an arrangement, in the zoom lens according to Japanese Patent Application Laid-open Publication No. 2011-232624, by an interchangeable lens application, at the time of zooming, a focal length changes from 40 mm to 150 mm, and an F-number is in a range of 4˜5.6 in a zoom range. Furthermore, in the zoom lens according to Japanese Patent Application Laid-open Publication No. 2011-232624, a resin material having a high abnormal dispersibility is used, thereby making a focusing lens unit light-weight, and facilitating correction of chromatic aberration.
However, in each of the zoom lenses according to Japanese Patent Application Laid-open Publication No. 2012-47814, Japanese Patent No. 5068238, and Japanese Patent Application Laid-open Publication No. 2011-232624, the F-number at a telephoto end is about 5.6 which is large, and is a dark lens.
Meanwhile, in Japanese Patent Publication No. 4560745 and Japanese Patent Publication No. 3466711, high-magnification zoom lenses for a compact camera have been disclosed. The zoom lens disclosed in Japanese Patent Publication No. 4560745 is a six-unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, a negative refractive power, a negative refractive power, and a positive refractive power. In the zoom lens disclosed Japanese Patent Publication No. 4560745, at the time of zooming, each lens unit moves.
According to such an arrangement, the zoom lens disclosed in Japanese Patent Publication No. 4560745 is a high-magnification zoom lens for which, at the time of zooming, a focal length changes (focal length is standardized) in a range of 1 mm-28 mm, and an F-number is in a range of about 1.8-3.6 in a zoom range.
The zoom lens disclosed in Japanese Patent Publication No. 3466711 is a five-unit zoom lens having an arrangement of refractive power in order from an object side, a positive refractive power, a negative refractive power, a positive refractive power, a negative refractive power, and a positive refractive power. In the zoom lens disclosed in Japanese Patent Publication No. 3466711, at the time of zooming, a second lens unit and a fourth lens unit move.
According to such an arrangement, the zoom lens disclosed in Japanese Patent Publication No. 3466711 is a high-magnification zoom lens for which, at the time of zooming, a focal length changes (focal length is normalized) in a range of 1 mm˜20 mm, and an F-number is in a range of about 1.8˜3.6 in a zoom range.
Here, it is not possible to use the zoom lenses disclosed in the aforementioned patent publications as they are, as an interchangeable lens.